purification =100 Si-So Si and So are the Si concentrations of pollutant in the inlet and outlet flows sludgeload FS, Fi is the rate of incoming water to a reactor volume Vreact with sludge concentration Xreact react Sludge age (days) 脉= δis the SF separation factor Si Si So purification − =100 react react i i V X FS sludgeload = i F V x react   = Si and So are the concentrations of pollutant in the inlet and outlet flows Fi is the rate of incoming water to a reactor volume Vreact with sludge concentration Xreact Sludge age (days) δ is the separation factor